


Solemnly Swear

by FantasticNumberNine



Series: John Watson and the Prisoner of Azkaban [7]
Category: Harry Potter - J. K. Rowling, Sherlock (TV)
Genre: AU, Christmas, Crossover, Gen, Hogsmeade, Honeydukes, Maurader's Map, Potterlock, Presents, Secret Passages, Secrets Revealed, Three Broomsticks
Language: English
Status: Completed
Published: 2015-04-05
Updated: 2015-04-05
Packaged: 2018-03-21 11:06:34
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,510
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3689946
Author URL: https://archiveofourown.org/users/FantasticNumberNine/pseuds/FantasticNumberNine
Summary: <blockquote class="userstuff">
              <p>An illicit visit to Hogsmeade has John swearing vengeance on Sirius Black, and cheering him up is made difficult for Greg and Mycroft, who engage in their own, personal, civil war...</p>
            </blockquote>





	Solemnly Swear

**Author's Note:**

> What a ridiculously dramatic summary... This isn't actually Days of Our Lives... But gods, this enstallment fought me for every inch. On a positive note, John, Greg, and Mycroft's next Christmas is pretty much written... :)

Professor Lupin asked about John's broom after their next Defense class, but John had another subject in mind.

"Did you hear about the dementors?"

"Yes, I did. They've been growing restless for some time... I suppose they are the reason you fell?"

"Yes," John clenched his fists and looked away, then, " _Why_? Why do they affect me like that? Am I just--"

"It has nothing to do with weakness, John," Professor Lupin interrupted quickly. "The dementors affect you worse than others because there are horrors in your past that the others don't have, you have nothing to feel ashamed of."

John stared hard at Lupin's desk, his throat tight. "I can hear Voldemort murdering my mum, when they get near me."

There was a moment of awkward silence, as Lupin aborted whatever movement his arm had been attempting, and John mentally kicked himself for admitting that particular truth.

"You--" John coughed. "You made the dementor on the train back off..."

"I--yes, there are, certain defenses one can use," said Lupin. "You understand, there was only one dementor on the train, the more there are, the more difficult it becomes to fight back."

"But you can teach me?" John asked, newly hopeful.

Lupin hesitated before saying, "Alright. I'll try and help. But it will have to wait until after the holidays--I chose a very inconvenient time to fall ill."

John's mood rose quickly through November, with the promise of anti-dementor lessons from Lupin, and Ravenclaw flattening Hufflepuff in their Quidditch match putting Gryffindor back in the running. The buzz of Christmas took over the castle as they passed into December and both Greg and Mycroft were staying at Hogwarts for the holiday.

On the last weekend before term let out there would be a Hogsmeade trip--news that delighted everyone except John. Already resigned to being the only third year staying behind, again, he borrowed _Which Broomstick_ from Wood to find himself a new broom.

John walked Greg and Mycroft down to the entrance hall the morning of the Hogsmeade trip, waving goodbye as they walked away through the snow that had begun to fall.

With a sigh, he turned and started back up to Gryffindor Tower.

"Psst--John!"

Halfway along the third floor, Fred and George beckoned him into an empty classroom (a show of how bored John was already with his day, trusting himself alone with the twins).

"Early Christmas present for you, John," George beamed at him.

Fred pulled something from his cloak with a flourish and laid it on one of the desks--a blank square of very worn parchment. John stared at it, then up at Fred and George.

"Thanks... I've always wanted an old bit of parchment..." 

"A bit of old parchment!" Fred exclaimed, closing his eyes with a mortally offended grimace. "George!"

George pulled out his wand and lightly tapped the parchment, saying, " _I solemnly swear that I am up to no good._ "

Immediately, thin lines of dark ink began to spread across the parchment, joking and crisscrossing each other on the page. Words blossomed across the top, curly and elegant to proclaim:

_Messrs. Moony, Wormtail, Padfoot, and Prongs_  
_Purveyors of Aids to Magical Mischief-Makers_  
_are proud to present_  
_THE MARAUDER'S MAP_

John felt his jaw drop as he stared at the amazingly detailed map of Hogwarts--something he'd have traded his wand for during the first weeks of his first year--it included all the passages he'd learned so far and even more he'd never known existed. His finger traced one near where three dots, labeled Fred Lestrade, George Lestrade, and John Watson, as it led out of the castle--

"Right into Hogsmeade," said Fred. "There are seven passages to Hogsmeade. Filch knows about these four, but we know we're the only ones who know about _these_ \--"

"Don't bother with the one behind the mirror, it caved in sometime after last winter. We're also pretty sure no one's used this one either, seeing as the Whomping Willow's planted right over the entrance. But this one, right outside, leads straight to Honeyduke's cellar."

"Moony, Wormtail, Padfoot, and Prongs..." Fred sighed.

"We owe them so much," George patted the map heading.

"Also, don't forget to wipe it clean after you've used it--"

"--Or anyone can read it--"

"Just tap it and say, 'Mischief Managed!' and it'll go blank."

John stood there, staring at the map after the twins had left, tracing the passage into Honeydukes. There were a thousand good reasons why he, John Watson, should not go sneaking into Hogsmeade. 

But...

Honeyduke's was so crowded with Hogwarts students that no one looked twice at John. He slipped through them quietly, though no one noticed his snort when he imagined Dudley's face if he could see John now.

Squeezing through some sixth years, John saw Greg and Mycroft standing under a sign in the far corner that read _Unusual Tastes_. John sneaked up behind them as they were looking at a tray of blood-flavored lollipops.

"Ugh, John won't want one of those. I expect they're made with vampires in mind," Mycroft said.

"How about these?" Greg asked, holding up a jar of Cockroach Clusters for Mycroft to inspect.

"Definitely not," said John.

Greg dropped the jar, catching it again just before it shattered on the flagstones.

"John!" Mycroft squeaked. "What are you doing here? How--no, you found a passage, underground?"

John told them quietly about the Marauder's Map.

"While I understand your desire to see Hogsmeade overrode any sense of responsibility you once possessed," said Mycroft, rubbing his palm against his face. "Please tell me you intend to turn the map over to Professor McGonagall when we return to the castle."

"What? No!" 

"Are you mad, Myc?" Greg exclaimed, "Hand in something this brilliant? Why not fork over his invisibility cloak too!"

"He might as well if he isn't going to use it on his illicit visitations to the village--"

"--You're bloody mental--"

"--And what about Sirius Black?" Mycroft turned again to face John, looking him sternly in the eye. "One of those passages could be how he gets into the castle; the teachers need to know, John."

"Because they've been _ever so_ helpful in the past?" John crossed his arms over his chest, not about to let Mycroft make him feel guilty about keeping this secret.

Mycroft looked away first, not quite hiding a faint look of pity. John stuck out his chin.

"Are you going to report me?" John asked.

Mycroft swung his head to stare at him, "No! Though, I really ought to. What if Sirius Black turned up, today? Who would know you needed protection?"

"You would, _obviously_ ," Greg said with a snort. "Come on, Myc, it's Christmas!"

Hogsmeade looked like a Christmas card and felt like a freezer. Unlike Greg and Mycroft, John didn't have his cloak--or gloves, or a scarf...

"How about this," Greg said through clattering teeth, "Let's go for a butterbeer in the Three Broomsticks, warm up a bit."

Which is how John found himself sitting under a table and peering wide-eyed through chair legs, legs, and a Christmas tree, as Professors McGonagall and Flitwick, Hagrid, Cornelius Fudge, and Madame Rosemerta discussed Sirius Black--John's godfather. 

"John?" 

Greg slid under the table beside him and Mycroft had leaned over to see him. Neither could think of anything to say.

John wasn't entirely certain how he'd made it back to his bed in Gryffindor Tower, and he was very confused by how empty he found the Common Room the next day when he came down just before lunch. Only Mycroft, with his homework spread across three tables, and Greg, who was dropping Peppermint Toad crumbs fastidiously over the three tables, were present.

"Where is everyone?" 

Greg smushed the last of his crumbs onto what John thought might be their latest Astronomy assignment as he spun to face him.

"They're gone, it's the first day of holidays, remember?" Greg watched John closely. "I was just about to go wake you up, it's nearly lunchtime."

"You don't look so well, John," Mycroft observed, stepping closer to John.

"Must be really bad for you to comment on it."

"John, we know you must be very upset about what we heard yesterday--"

"Drop it, Mycroft," John growled, pushing past Mycroft.

"You can't truly be thinking of going after Black--" Mycroft grabbed John's arm. "Even Gregory would never do anything so monumentally stupid!"

"Oi..."

"Well, bravery _is_ the kindest word for stupidity--"

Mycroft narrowed his eyes, "Going after Black isn't bravery, it's suicide. This isn't about _bravery_ though, is it, John? This is about vengeance."

John pulled his arm free.

"You have no idea--" his hands clenched at his sides, and his teeth ground harshly against each other. "Moriarty knows. He said it, he'd hunt Black down himself--"

"Wait," Greg interjected loudly. "You're going to do what _Jim bloody Moriarty_ wants instead of listening to what we--your _friends_ \--are trying to say? Moriarty, John! Who said that to you hoping you'd get yourself blown to pieces like Pettigrew before he has to play against you in the next Quidditch match!"

"John," Mycroft's voice was especially quiet after Greg's shouting. "Your parents died saving your life. Do you really think they would want you to go after Black?"

There was a short moment of tense silence before John snapped out, "I'm never going to know what they'd have wanted, am I? Thanks to Black, I've never spoken to them."

The following silence lasted much longer, as John stared into the fire, his anger cooling rapidly despite his declarations of revenge. Mycroft crouched down nearby with a concerned glance at Greg and began to pet Crookshanks, who stretched luxuriously under his ministrations. 

Greg shifted awkwardly. "Look, it's nearly Christmas, yeah? Let's go visit Hagrid, we haven't seen him in ages!"

But Greg's hope of lifting their collective spirit at Hagrid's was a vain one, and Hagrid spent their whole visit sobbing into a tablecloth-sized handkerchief. Buckbeak had been sentenced to death, and even their promise to help him with the defense had no significant effect--though it was suitable enough to distract John from brooding over Black, and the three of them spent the last few days before Christmas pouring over texts in the library that might help Hagrid.

On Christmas morning, John woke to Greg's pillow being thrown with distressing accuracy at his face.

"Oi! Presents!"

"Gregory, John is hardly going to learn to enjoy any holiday whereupon he is woken up by your projectile alarm clocks, goose-feather stuffed or otherwise," Mycroft drawled lazily.

John grinned in the semi-darkness--Greg was already ripping through his presents as Mycroft went to open the dormitory door, letting Crookshanks inside. 

"Another jumper from Mum... Maroon again, of course. See if you've got them!

They had, John's was scarlet with a golden Gryffindor lion knitted on the front. Mycroft's was plum colored this year, with crossed wands emitting sparks done in silver yarn. 

There was a strange, long and thin, package lying underneath John's remaining gifts, and John pulled it to the top, unwrapping it slowly. He gasped loudly when he finally revealed the magnificent, gleaming broomstick.

Greg leapt up beside him, "I don't believe it!"

It was a Firebolt, and it glittered in John's reverent hands. It vibrated and John it go slowly, his eyes taking in every perfect detail, as it hung in midair, begging to be flown.

"Who sent it?" Greg whispered.

John and Greg ripped at the wrapping, looking for a card, missing the contemplative and suspicious look Mycroft was giving the Firebolt.

"Nothing! Blimey, who'd spend that much on you?"

John was stunned. "Not the Dursley's, I know that much."

"Dumbledore? He did give you the Invisibility Cloak," said Greg, walking around the Firebolt in awe.

"He can't go giving students broomsticks, never mind a _Firebolt_!" 

Greg laughed, "John! John, _Moriarty_! Wait till he _sees_ you on this! He'll be sick as a pig!" He fell backwards into Mycroft's bed, giggling madly.

John was smiling as he ran a hand along the Firebolt. "But, _who_?"

"Myc! Why aren't you laughing?" 

"Neither of you find it odd? This is supposed to be quite a good broom, and likely very expensive--"

Greg sat up, affronted. " _Quite a good broom_! Myc! It's the best broom there is!"

"--So who would send John something so expensive and supposedly brilliant as this, and not bother to tell him who they are?"

"Who cares?" Greg draped himself on John's bed. "Listen, John, can I have a go on it? After you, obviously, but... Can I?"

"I don't think anyone should be riding that broom just--"

"Oh yeah, course, John's not really for riding the world's best racing brooms, he prefers to use them for _sweeping_ ," Greg scoffed. 

Mycroft didn't have time to reply, as in the next moment, Crookshanks sprang onto Greg's chest.

"AGH! MYC! GET--HIM--OUT--OF--HERE!" Greg bellowed, falling off of John's bed as Crookshanks ripped at his pajamas.

"Gregory--!"

In the chaos, John's trunk was upturned and a shrill whistling noise filled the room, and Crookshanks let go of Greg, who was struggling to hold onto Scabbers out of reach. Mycroft was able to grab Crookshanks, as John snatched the whirling Pocket Sneakoscope from where it had fallen free from its sick prison. 

Cradling Scabbers against his tattered pajama covered chest, Greg glared darkly at Mycroft. "You get that bloody cat out of here, Myc!"

Mycroft opened his mouth to argue, but John cut him off with a look, and he stormed out.

John stuffed the Pocket Sneakoscope back into Uncle Vernon's old socks and buried it at the bottom of his trunk.

"He's not looking too good, is he?" John nodded at Scabbers.

"It's stress!" Snapped Greg. "He'd be fine if that ruddy stupid fur all left him alone!"

John wasn't too sure, the woman at the Magical Menagerie had mentioned rats only living three years, and Scabbers had lived much longer than that. And, despite all of Greg's complaints to his uselessness, John was certain Greg would be miserable when Scabbers died.

Dinner started out as a tense affair, with John sitting cautiously between his two friends, but several hours later, after being stuffed full of delicious Christmas dinner and wearing their party hats, John and Greg returned to Gryffindor Tower to fawn over the Firebolt--leaving Mycroft, who wanted a quick word with McGonagall, behind.

John and Greg hadn't been staring too long before McGonagall entered the Common Room; Mycroft watched awkwardly behind her, as the Professor confiscated the Firebolt, despite John's and Greg's loud complaints.

John stood, stock still and staring at the portrait hole after McGonagall left, but Greg rounded almost immediately on Mycroft.

" _What did you go running to McGonagall for?_ "

Mycroft hands curled into tight fists at his side as he stuck out his chin, effectively looking down his nose at Greg with practiced superiority.

"Because, and Professor McGonagall agrees, that broom was in all probability sent to John by Sirius Black!"

**Author's Note:**

> Also. This was much longer than intended. Which is fine, probably. Just unexpected.


End file.
